Air-conditioner systems and cooling systems use a variety of refrigerants, which are likely to leak outside during use. In such a case, a refrigerant-leakage spot needs to be found. Typically, the leakage of the refrigerant is detected simply depending on the presence or absence of bubbles formed of soapy water sprayed onto pipes and joints in the system. These days, a leakage-detecting method using a fluorescent agent has been developed and a refrigerant-leakage-detecting fluorescent agent is sometimes provided in a receiver dryer in a refrigeration cycle in an automobile air-conditioner.
According to Patent Literatures 1 and 2, a fluorescence dye containing a polycyclic aromatic compound such as xanthene and perylene is used in a cooling system to detect the leakage of a refrigerant.